Rhodium-Catalyzed Aldehyde Arylation via Formate-Mediated

Communication Cite This: J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

pubs.acs.org/JACS

Rhodium-Catalyzed Aldehyde Arylation via Formate-Mediated Transfer Hydrogenation: Beyond Metallic Reductants in Grignard/ Nozaki−Hiyami−Kishi-Type Addition Robert A. Swyka,†,∥ Wandi Zhang,†,∥ Jeffery Richardson,‡ J. Craig Ruble,§ and Michael J. Krische*,† †

Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States Discovery Chemistry Research and Technologies, Eli Lilly and Company Limited, Erl Wood Manor, Windlesham, Surrey GU20 6PH, United Kingdom § Discovery Chemistry Research and Technologies, Eli Lilly and Company, Indianapolis, Indiana 46285, United States J. Am. Chem. Soc. Downloaded from pubs.acs.org by UNIV OF WINNIPEG on 01/29/19. For personal use only.

‡

S Supporting Information *

ABSTRACT: The first intermolecular carbonyl arylations via transfer hydrogenative reductive coupling are described. Using rhodium catalysts modified by tBu2PMe, sodium formate-mediated reductive coupling of aryl iodides with aldehydes occurs in a chemoselective fashion in the presence of protic functional groups and lower halides. This work expands the emerging paradigm of transfer hydrogenative coupling as an alternative to preformed carbanions or metallic reductants in CX addition.

S

ince the seminal work of Butlerov (1863),1a,b Reformatsky (1887),1c and Grignard (1900),1d the use of pre-formed organometallic reagents in carbonyl addition has remained a cornerstone of chemical synthesis.2 Countless protocols for the addition of non-stabilized carbanions and their equivalents (e.g., arylboron reagents)3f,g to carbonyl compounds and imines now exist, including enantioselective methods.3 Nevertheless, the requisite organometallic nucleophiles complicate large-volume applications due to issues of safety, the frequent requirement of cryogenic conditions, and the separation/ disposal of metallic byproducts. While metal-catalyzed reductive coupling represents an alternative to discrete organometallic reagents in carbonyl addition, the terminal reductants often utilized in such processes are metallic (Zn, Mn), toxic (CrCl2), pyrophoric (BEt3, ZnEt2, AlMe3), or expensive/mass-intensive (R3SiH).4 Using hydrogen, 2-propanol, and formic acid, which are relatively benign, inexpensive, low-molecular-weight reductants, diverse catalytic enantioselective carbonyl and imine reductive coupling reactions were developed in our laboratory,4b,d,e,g,i,l including aldol additions,5a vinylations,5b allylations,4l,5c−e and propargylations.4l,5f,g Here, we report the f irst examples of intermolecular carbonyl arylation via metal-catalyzed transfer hydrogenation, representing the f irst intermolecular carbonyl−aryl halide reductive couplings beyond metallic reductants (Figure 1).6,7 Aside from the Nozaki−Hiyami−Kishi reaction,6,7 surprisingly few intermolecular metal-catalyzed aryl halide−aldehyde reductive couplings have been reported, all of which are mediated by elemental zinc8 (or an Mn−Cr alloy)8c or are conducted electrochemically.9 Reductive aldehyde arylations © XXXX American Chemical Society

Figure 1. Classical carbonyl arylation and related catalytic reductive couplings.

via hydrogenation or transfer hydrogenation have not been described, almost certainly due to competing hydrogenolysis of the aryl halide.10 Despite this lack of precedent, a hydrogenmediated Grignard-type cyclization was recently developed in our laboratory.11 While these conditions were not applicable to intermolecular carbonyl reductive couplings, related redoxneutral aryl halide−aldehyde couplings to form ketone products have been reported.12 In these processes, Ar−X oxidative addition is followed by carbonyl insertion to form a metal alkoxide, which upon β-hydride elimination and H−X reductive elimination returns the metal to its low-valent form. It was posited that interception of the metal alkoxide derived upon carbonyl arylation by 2-propanol or a formate salt might enable reductive arylation to form secondary alcohol products. Received: December 21, 2018

A

DOI: 10.1021/jacs.8b13652 J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Communication

Journal of the American Chemical Society Table 1. Selected Optimization Experiments in the Rhodium-Catalyzed Transfer Hydrogenative Aldehyde Arylationa

Table 2. Rhodium-Catalyzed Transfer Hydrogenative Coupling of Aldehydes 1a−1u and Aryl Iodides 2a−2u To Form Products of Reductive Arylation, 3a−3ua

a

Yields are of material isolated by silica gel chromatography. Bu2PMe·HBF4 was employed as ligand precursor. PtBu3 was used as a 1.0 M solution in toluene. Lithium formate was used as the monohydrate. The loading of bidentate ligands was 5.5 mol%. The loading of dimeric rhodium pre-catalysts was 2.5 mol%. See Supporting Information for further experimental details. bReaction was conducted without Cs2CO3. c75 °C in DME or 130 °C in diglyme. d2a (150 mol%). t

With this strategy in mind, piperonal 1a (100 mol%) and 4iodotoluene 2a (200 mol%) were exposed to 2-propanol or sodium formate in the presence of diverse palladium or rhodium complexes. Using the catalyst derived from Rh(acac)(CO)2 (5 mol%) and PCy3 (11 mol%) with NaO2CH (300 mol%) as reductant and Cs2CO3 (100 mol%) as base in dioxane (0.2 M) at 130 °C, the desired reductive coupling product 3a was formed in 12% isolated yield (Table 1, entry 1). A range of other ligands were evaluated under these conditions (Table 1, entries 1−8). It was found that the catalyst formed in situ from Rh(acac)(CO)2 (5 mol%) and t Bu2PMe (11 mol%) delivered the benzhydryl alcohol 3a in 40% isolated yield (Table 1, entry 8). Increased efficiencies were observed for reactions conducted in tert-amyl alcohol (Table 1, entry 9) and dimethoxyethane (Table 1, entry 10), which provided 64% and 72% isolated yields of 3a, respectively. Deviation from the latter conditions did not improve the yield of 3a (Table 1, entries 11−20). Lower loadings of NaO2CH or 2a decreased the isolated yield of 3a. NHC-modified rhodium complexes did not promote reductive coupling.8g To evaluate reaction scope, optimal conditions identified for the formation of 3a were applied to aldehydes 1a−1u and aryl iodides 2a−2u (Table 2). Both aromatic (1a−1p) and aliphatic aldehydes (1q−1u) underwent reductive coupling efficiently, and diverse functional groups, including those that are incompatible with main-group organometallic reagents, were tolerated. As illustrated in the formation of compounds

a

All reactions were performed on a 0.20 mmol scale. Yield of material isolated by silica gel chromatography. See Supporting Information for further experimental details. b[RhCl(CO)2]2 (2.5 mol%) was used.

3b, 3f, 3j, 3o, and 3p, aryl iodides may be activated in the presence of aryl chlorides and bromides. Additionally, as illustrated by the formation of 3c−3e, 3h, 3j−3l, 3n, and 3o, fluorine-containing functional groups are tolerated. Notably, 2fluoro- and 2-chloro-containing 1-iodobenzenes 2l and 2o were converted to adducts 3l and 3o, respectively, without competing aryne formation.13 The formation of products 3g, 3i and 3s, which incorporate alcohol, carbamate, and sulfonamide groups, respectively, demonstrates the tolerance of acidic OHand NH-containing functional groups. Adducts 3e, 3h, and 3o, which incorporate aromatic N-heterocycles, are formed efficiently, as are adducts 3i and 3m, which contain methyl sulfide and methyl ester moieties. The tolerance of orthosubstituted iodides, as demonstrated by the formation of adducts 3c, 3e, 3j−3l, 3n−3p, 3r, and 3tin particular the formation of adduct 3c, derived from an ortho,orthoB

DOI: 10.1021/jacs.8b13652 J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Communication

Journal of the American Chemical Society

In summary, we report the first example of reductive carbonyl arylation using a non-metallic reductant, sodium formate. This process is non-cryogenic and can be applied in the presence of functional groups that are typically not compatible with traditional main-group organometallic reagents. This work, along with other hydrogen-transfermediated carbonyl reductive couplings developed in our laboratory, defines a departure from the use of pre-metalated reagents in chemical synthesis. Future studies will focus on development of related transfer hydrogenative couplings of vinylic and saturated alkyl halides.

Scheme 1. Proposed Catalytic Mechanism for RhodiumCatalyzed Transfer Hydrogenative Arylation Mediated by Formate

■

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.8b13652. Experimental procedures and spectral data (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*[email protected] ORCID

Jeffery Richardson: 0000-0002-4450-3828 Michael J. Krische: 0000-0001-8418-9709 Author Contributions ∥

R.A.S. and W.Z. contributed equally.

Notes

disubstituted mesityl iodideis also notable. Finally, linear and branched aliphatic aldehydes were converted to adducts 3q−3u without competing aldol dimerization. The primary side reactions observed are reduction of the aldehyde, dehydrohalogenation, or reductive dimerization of the aryl iodide and ketone formation.12 To gain insight into the catalytic cycle, deuterium labeling experiments were undertaken (eqs 1 and 2 in Scheme 1). Exposure of the aldehyde deuterio-1a to 4-iodotoluene 2a under standard reaction conditions resulted in the formation of deuterio-3a, which completely retains deuterium at the carbinol position (>95:5 2H) (eq 1). In a second experiment, aldehyde 1a and 4-iodotoluene 2a were subjected to standard reaction conditions using NaO2CD (eq 2). The product 3a did not incorporate deuterium. These results refute intervention of ketone intermediates that might arise via β-hydride elimination from the rhodium alkoxide derived upon carbonyl insertion into the aryl−rhodium bond.14 Exposure of aryl ketones to the standard reaction conditions results in only trace quantities of carbonyl reduction product. Based on the collective data, the following catalytic cycle is proposed (Scheme 1, bottom). Rhodium(I)-mediated aryl iodide oxidation addition15 delivers the arylrhodium(III) complex I. Aldehyde coordination precedes insertion of the aldehyde CO bond into the metal−aryl bond to form the rhodium(III) alkoxide II.14 Counterion exchange provides the rhodium(III) formate complex III, which upon β-hydride elimination releases CO2 and forms the alkoxyrhodium(III) hydride IV. Finally, O−H reductive elimination16 releases the product of carbonyl arylation and returns rhodium to its lowvalent form. The role of Cs2CO3 appears to extend beyond the deprotonation of tBu2PMe·HBF4. Lower isolated yields are observed when other carbonate bases are used or the loading of Cs2CO3 is decreased. Studies aimed at elucidating more precise details of the reaction mechanism are underway.

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The Robert A. Welch Foundation (F-0038) and the NIHNIGMS (RO1-GM069445) are acknowledged for generous financial support. Eli Lilly and Company is acknowledged for LIFA postdoctoral fellowship funding (R.A.S.).

■

REFERENCES

(1) (a) Butlerov, A. Studien über die Einfachsten Verbindungen der Organischen Chemie. Z. Chem. Pharm. 1863, 6, 484−497. (b) Butlerov, A. Z. Sur l’Alcool Pseudobuylique Tertiare ou Alcool Méthylique triméthylé. Bull. Soc. Chim. Fr. 1864, 2, 106−116. (c) Reformatsky, S. Neue Synthese Zweiatomiger Einbasischer Säuren aus den Ketonen. Ber. Dtsch. Chem. Ges. 1887, 20, 1210−1211. (d) Grignard, V. Sur Quelques Nouvelles Combinaisons Organométalliques du Magnèsium et Leur Application àdes Synthèses d’alcools et d’hydrocarbures. C. R. Hebd Seánces Acad. Sci., Ser. C 1900, 130, 1322−1324. (2) Comprehensive Organic Synthesis, 2nd ed.; Knochel, P., Molander, G. A., Eds.; Elsevier: Oxford, 2014; Vols. 1 and 2. (3) For selected reviews on catalytic enantioselective carbonyl addition, see: (a) Soai, K.; Shibata, T. Alkylation of Carbonyl Groups. In Comprehensive Asymmetric Catalysis I−III; Jacobsen, E. N., Pfaltz, A., Yamamoto, H., Eds.; Springer-Verlag: Berlin/Heidelberg, Germany, 1999; Vol. 2, pp 911−922. (b) Kobayashi, S.; Ishitani, H. Catalytic Enantioselective Addition to Imines. Chem. Rev. 1999, 99, 1069−1094. (c) Pu, L.; Yu, H.-B. Catalytic Asymmetric Organozinc Additions to Carbonyl Compounds. Chem. Rev. 2001, 101, 757−824. (d) Trost, B. M.; Weiss, A. H. The Enantioselective Addition of Alkyne Nucleophiles to Carbonyl Groups. Adv. Synth. Catal. 2009, 351, 963−983. (e) Garcia, C.; Martin, V. S. Asymmetric addition to ketones: enantioselective formation of tertiary alcohols. Curr. Org. Chem. 2006, 10, 1849−1889. (f) Miyaura, N. Celebrating 20 Years of SYNLETT-Special Account On Palladium (II)-Catalyzed Additions of Arylboronic Acids to Electron-Deficient Alkenes, Aldehydes, Imines, and Nitriles. Synlett 2009, 2009, 2039−2050. (g) Tian, P.; C

DOI: 10.1021/jacs.8b13652 J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Communication

Journal of the American Chemical Society Dong, H.-Q.; Lin, G.-Q. Rhodium-Catalyzed Asymmetric Arylation. ACS Catal. 2012, 2, 95−119. (4) For selected reviews on metal-catalyzed reductive coupling, see: (a) Montgomery, J. Nickel-Catalyzed Reductive Cyclizations and Couplings. Angew. Chem., Int. Ed. 2004, 43, 3890−3908. (b) Iida, H.; Krische, M. J. Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen. Top. Curr. Chem. 2007, 279, 77−104. (c) Jeganmohan, M.; Cheng, C.-H. Cobalt-and Nickel-Catalyzed Regio-and Stereoselective Reductive Coupling of Alkynes, Allenes, and Alkenes with Alkenes. Chem. - Eur. J. 2008, 14, 10876−10886. (d) Hassan, A.; Krische, M. J. Unlocking Hydrogenation for C−C Bond Formation: A Brief Overview of Enantioselective Methods. Org. Process Res. Dev. 2011, 15, 1236− 1242. (e) Moran, J.; Krische, M. J. Formation of C-C Bonds via Ruthenium Catalyzed Transfer Hydrogenation. Pure Appl. Chem. 2012, 84, 1729−1739. (f) Moragas, T.; Correa, A.; Martin, R. MetalCatalyzed Reductive Coupling Reactions of Organic Halides with Carbonyl-Type Compounds. Chem. - Eur. J. 2014, 20, 8242−8258. (g) Ketcham, J. M.; Shin, I.; Montgomery, T. P.; Krische, M. J. Catalytic Enantioselective C-H Functionalization of Alcohols by Redox-Triggered Carbonyl Addition: Borrowing Hydrogen, Returning Carbon. Angew. Chem., Int. Ed. 2014, 53, 9142−9150. (h) Everson, D. A.; Weix, D. J. Cross-Electrophile Coupling: Principles of Reactivity and Selectivity. J. Org. Chem. 2014, 79, 4793−4798. (i) Nguyen, K. D.; Park, B. Y.; Luong, T.; Sato, H.; Garza, V. J.; Krische, M. J. Metal-catalyzed reductive coupling of olefin-derived nucleophiles: Reinventing carbonyl addition. Science 2016, 354, aah5133. (j) Wang, X.; Dai, Y.; Gong, H. Nickel-Catalyzed Reductive Couplings. Top. Curr. Chem. 2016, 374, 1. (k) Kim, S. W.; Zhang, W.; Krische, M. J. Catalytic Enantioselective Carbonyl Allylation and Propargylation via Alcohol-Mediated Hydrogen Transfer: Merging the Chemistry of Grignard and Sabatier. Acc. Chem. Res. 2017, 50, 2371−2380. (l) Holmes, M.; Schwartz, L. A.; Krische, M. J. Intermolecular Metal-Catalyzed Reductive Coupling of Dienes, Allenes, and Enynes with Carbonyl Compounds and Imines. Chem. Rev. 2018, 118, 6026−6052. (5) For seminal examples of enantioselective hydrogenative and transfer hydrogenative aldol additions, vinylations, allylations, and propargylations, see: (a) Bee, C.; Han, S. B.; Hassan, A.; Iida, H.; Krische, M. J. Diastereo- and Enantioselective Hydrogenative Aldol Coupling of Vinyl Ketones: Design of Effective Monodentate TADDOL-Like Phosphonite Ligands. J. Am. Chem. Soc. 2008, 130, 2746−2747. (b) Ngai, M.-Y.; Barchuk, A.; Krische, M. J. Enantioselective Iridium-Catalyzed Imine Vinylation: Optically Enriched Allylic Amines via Alkyne−Imine Reductive Coupling Mediated by Hydrogen. J. Am. Chem. Soc. 2007, 129, 12644− 12645. (c) Kim, I. S.; Ngai, M.-Y.; Krische, M. J. Enantioselective Iridium-Catalyzed Carbonyl Allylation from the Alcohol or Aldehyde Oxidation Level Using Allyl Acetate as an Allyl Metal Surrogate. J. Am. Chem. Soc. 2008, 130, 6340−6341. (d) Kim, I. S.; Ngai, M.-Y.; Krische, M. J. Enantioselective Iridium-Catalyzed Carbonyl Allylation from the Alcohol or Aldehyde Oxidation Level via Transfer Hydrogenative Coupling of Allyl Acetate: Departure from Chirally Modified Allyl Metal Reagents in Carbonyl Addition. J. Am. Chem. Soc. 2008, 130, 14891−14899. (e) Kim, I. S.; Han, S. B.; Krische, M. J. anti-Diastereo- and Enantioselective Carbonyl Crotylation from the Alcohol or Aldehyde Oxidation Level Employing a Cyclometallated Iridium Catalyst: α-Methyl Allyl Acetate as a Surrogate to Preformed Crotylmetal Reagents. J. Am. Chem. Soc. 2009, 131, 2514−2520. (f) Geary, L. M.; Woo, S. K.; Leung, J. C.; Krische, M. J. Diastereoand Enantioselective Iridium-Catalyzed Carbonyl Propargylation from the Alcohol or Aldehyde Oxidation Level: 1,3-Enynes as Allenylmetal Equivalents. Angew. Chem., Int. Ed. 2012, 51, 2972−2976. (g) Woo, S. K.; Geary, L. M.; Krische, M. J. Enantioselective Carbonyl Propargylation by Iridium-Catalyzed Transfer Hydrogenative Coupling of Alcohols and Propargyl Chlorides. Angew. Chem., Int. Ed. 2012, 51, 7830−7834. (6) For selected examples of intermolecular Nozaki−Hiyama−Kishi arylation, see: (a) Takai, K.; Kimura, K.; Kuroda, T.; Hiyama, T.;

Nozaki, H. Selective Grignard-Type Carbonyl Addition of Alkenyl Halides Mediated by Chromium(II) Chloride. Tetrahedron Lett. 1983, 24, 5281−5284. (b) Fürstner, A.; Shi, N. A Multicomponent Redox System Accounts for the First Nozaki−Hiyama−Kishi Reactions Catalytic in Chromium. J. Am. Chem. Soc. 1996, 118, 2533−2534. (c) Fürstner, A.; Shi, N. Nozaki−Hiyama−Kishi Reactions Catalytic in Chromium. J. Am. Chem. Soc. 1996, 118, 12349−12357. (d) Namba, K.; Wang, J.; Cui, S.; Kishi, Y. Surprisingly Efficient Catalytic Cr-Mediated Coupling Reactions. Org. Lett. 2005, 7, 5421− 5424. (7) For selected reviews on the Nozaki−Hiyama−Kishi reaction, see: (a) Fürstner, A. Carbon−Carbon Bond Formations Involving Organochromium(III) Reagents. Chem. Rev. 1999, 99, 991−1046. (b) Tian, Q.; Zhang, G. Recent Advances in the Asymmetric Nozaki− Hiyama−Kishi Reaction. Synthesis 2016, 48, 4038−4049. (8) For intermolecular metal-catalyzed aryl halide−aldehyde reductive coupling employing metallic reductants, see the following. Nickel: (a) Majumdar, K. K.; Cheng, C.-H. Ni(II)/Zn-Mediated Chemoselective Arylation of Aromatic Aldehydes: Facile Synthesis of Diaryl Carbinols. Org. Lett. 2000, 2, 2295−2298. (b) Rayabarapu, D. K.; Chang, H. T.; Cheng, C.-H. Synthesis of Phthalide Derivatives Using Nickel-Catalyzed Cyclization of o-Haloesters with Aldehydes. Chem. - Eur. J. 2004, 10, 2991−2996. (c) Harnying, W.; Berkessel, A. Vinylation of Aldehydes Using Mn/Cr Alloy and a N4-Ligand/NiIICatalyst. Chem. - Eur. J. 2015, 21, 6057−6061. (d) Arendt, K. M.; Doyle, A. G. Dialkyl Ether Formation by Nickel-Catalyzed CrossCoupling of Acetals and Aryl Iodides. Angew. Chem., Int. Ed. 2015, 54, 9876−9880. (e) Asachenko, A. F.; Valaeva, V. N.; Kudakina, V. A.; Uborsky, D. V.; Izmer, V. V.; Kononovich, D. S.; Voskoboynikov, A. Z. Coupling of Aromatic Aldehydes with Aryl Halides in the Presence of Nickel Catalysts with Diazabutadiene Ligands. Russ. Chem. Bull. 2016, 65, 456−463. (f) Garcia, K. J.; Gilbert, M. M.; Weix, D. J. Nickel Catalyzed Addition of Aryl Bromides to Aldehydes To Form Hindered Secondary Alcohols. J. Am. Chem. Soc. 2019, DOI: 10.1021/jacs.8b13709, (preceding paper in this issue) . Rhodium: (g) Zhou, F.; Li, C.-J. The Barbier−Grignard-Type Arylation of Aldehydes Using Unactivated Aryl Iodides in Water. Nat. Commun. 2014, 5, 4254. (9) For electrochemical intermolecular aryl halide−aldehyde reductive couplings, see: (a) Durandetti, M.; Périchon, J.; Nédélec, J.-Y. Nickel- and Chromium-Catalyzed Electrochemical Coupling of Aryl Halides with Arenecarboxaldehydes. Tetrahedron Lett. 1999, 40, 9009−9013. (b) Durandetti, M.; Nédélec, J.-Y.; Perichon, J. An Electrochemical Coupling of Organic Halide with Aldehydes, Catalytic in Chromium and Nickel Salts. The Nozaki−Hiyama− Kishi Reaction. Org. Lett. 2001, 3, 2073−2076. (10) For reviews on the hydrogenolysis of organic halides, see: (a) Pinder, A. R. The Hydrogenolysis of Organic Halides. Synthesis 1980, 1980, 425−452. (b) Hudlicky, M. Reduction in Organic Chemistry in Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Elsevier Ltd., 1991; Vol. 8, pp 895−922. (c) Urbano, F. J.; Marinas, J. M. Hydrogenolysis of Organohalogen Compounds Over Palladium Supported Catalysts. J. Mol. Catal. A: Chem. 2001, 173, 329−345. (d) Sheldon, R. A.; van Bekkum, H. Fine Chemicals through Heterogeneous Catalysis; Wiley-VCH, Weinheim, Germany, 2001; pp 415−442. (e) Alonso, F.; Beletskaya, I. P.; Yus, M. Metal-Mediated Reductive Hydrodehalogenation of Organic Halides. Chem. Rev. 2002, 102, 4009−4092. (f) Chelucci, G.; Baldino, S.; Pinna, G. A.; Pinna, G. Synthetic Methods for the Hydrodehalogenation of Halogenated Heterocycles. Curr. Org. Chem. 2012, 16, 2921−2945. (11) Shin, I.; Ramgren, S. D.; Krische, M. J. Reductive Cyclization of Halo-Ketones to form 3-hydroxy-2-oxindoles via Palladium Catalyzed Hydrogenation: a Hydrogen-mediated Grignard addition. Tetrahedron 2015, 71, 5776−5780. (12) For redox-neutral catalytic aryl halide−aldehyde couplings to form ketone products, see the following. Palladium: (a) Satoh, T.; Itaya, T.; Miura, M.; Nomura, M. Palladium-Catalyzed Coupling Reaction of Salicylaldehydes with Aryl Iodides via Cleavage of the Aldehyde C−H Bond. Chem. Lett. 1996, 25, 823−824. (b) Ko, S.; D

DOI: 10.1021/jacs.8b13652 J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Communication

Journal of the American Chemical Society Kang, B.; Chang, S. Cooperative Catalysis by Ru and Pd for the Direct Coupling of a Chelating Aldehyde with Iodoarenes or Organostannanes. Angew. Chem., Int. Ed. 2005, 44, 455−457. (c) Takemiya, A.; Hartwig, J. F. Palladium-Catalyzed Synthesis of Aryl Ketones by Coupling of Aryl Bromides with an Acyl Anion Equivalent. J. Am. Chem. Soc. 2006, 128, 14800−14801. (d) Ruan, J.; Saidi, O.; Iggo, J. A.; Xiao, J. Direct Acylation of Aryl Bromides with Aldehydes by Palladium Catalysis. J. Am. Chem. Soc. 2008, 130, 10510−10511. (e) Zanardi, A.; Mata, J. A.; Peris, E. Palladium Complexes with Triazolyldiylidene. Structural Features and Catalytic Applications. Organometallics 2009, 28, 1480−1483. (f) Adak, L.; Bhadra, S.; Ranu, B. C. Palladium(0) Nanoparticle-catalyzed sp2 C−H Activation: A Convenient Route to alkyl−aryl Ketones by Direct Acylation of Aryl Bromides and Iodides with Aldehydes. Tetrahedron Lett. 2010, 51, 3811−3814. (g) Nowrouzi, N.; Motevalli, S.; Tarokh, D. PalladiumCatalyzed Direct C−H Arylation of 2-hydroxybenzaldehydes With Organic Halides in Neat Water. J. Mol. Catal. A: Chem. 2015, 396, 224−230. (h) Nowrouzi, N.; Tarokh, D. PdCl2/DABCO-Catalyzed Direct Arylation of 2-hydroxybenzaldehydes in H2O. J. Iran. Chem. Soc. 2016, 13, 1493−1497. (i) Suchand, B.; Satyanarayana, G. Palladium-Catalyzed Environmentally Benign Acylation. J. Org. Chem. 2016, 81, 6409−6423. (j) Wakaki, T.; Togo, T.; Yoshidome, D.; Kuninobu, Y.; Kanai, M. Palladium-Catalyzed Synthesis of Diaryl Ketones from Aldehydes and (Hetero)Aryl Halides via C−H Bond Activation. ACS Catal. 2018, 8, 3123−3128. Rhodium: (k) Ishiyama, T.; Hartwig, J. F. A Heck-Type Reaction Involving Carbon− Heteroatom Double Bonds. Rhodium(I)-Catalyzed Coupling of Aryl Halides with N-Pyrazyl Aldimines. J. Am. Chem. Soc. 2000, 122, 12043−12044. (l) Rao, M. L.; Ramakrishna, B. S. RhodiumCatalyzed Directing-Group-Assisted Aldehydic C−H Arylations with Aryl Halides. Eur. J. Org. Chem. 2017, 2017, 5080−5093. Nickel: (m) Huang, Y.-C.; Majumdar, K. K.; Cheng, C.-H. Nickel-Catalyzed Coupling of Aryl Iodides with Aromatic Aldehydes: Chemoselective Synthesis of Ketones. J. Org. Chem. 2002, 67, 1682−1684. (n) Nowrouzi, N.; Zarei, M.; Roozbin, F. First Direct Access to 2hydroxybenzophenones via Nickel-Catalyzed Cross-Coupling of 2Hydroxybenzaldehydes with Aryl Iodides. RSC Adv. 2015, 5, 102448−102453. Photo-redox: (o) Zhang, X.; MacMillan, D. W. C. Direct Aldehyde C−H Arylation and Alkylation via the Combination of Nickel, Hydrogen Atom Transfer, and Photoredox Catalysis. J. Am. Chem. Soc. 2017, 139, 11353−11356. Cobalt: (p) Hu, Y. L.; Wu, Y. P.; Lu, M. Co (II)-C12 Alkyl Carbon Chain Multi-Functional Ionic Liquid Immobilized on Nano-SiO2 NanoSiO2@CoCl3-C12IL as an Efficient Cooperative Catalyst for C−H Activation by Direct Acylation of Aryl Halides with Aldehydes. Appl. Organomet. Chem. 2018, 32, e4096. (13) For the magnesium-mediated generation of benzyne from 1bromo-2-fluorobenzene, see: Wittig, G. Triptycene. Org. Synth. 1959, 39, 75. (14) For insertion of aldehyde CO π-bonds into arylrhodium σ-bonds and related β-aryl eliminations, see: (a) Krug, C.; Hartwig, J. F. Direct Observation of Aldehyde Insertion into Rhodium−Aryl and − Alkoxide Complexes. J. Am. Chem. Soc. 2002, 124, 1674−1679. (b) Zhao, P.; Incarvito, C. D.; Hartwig, J. F. Direct Observation of βAryl Eliminations from Rh(I) Alkoxides. J. Am. Chem. Soc. 2006, 128, 3124−3125. (15) For studies on the oxidative addition of aryl halides to rhodium(I) complexes, see the following: Monophosphine complexes: (a) Jiao, Y.; Brennessel, W. W.; Jones, W. D. Oxidative Addition of Chlorohydrocarbons to a Rhodium Tris(pyrazolyl)borate Complex. Organometallics 2015, 34, 1552−1566. (b) Townsend, N. S.; Chaplin, A. B.; Abu Naser, M.; Thompson, A. L.; Rees, N. H.; Macgregor, S. A.; Weller, A. S. Reactivity of the Latent 12-Electron Fragment [Rh(PiBu3)2]+ with Aryl Bromides: Aryl−Br and Phosphine Ligand C−H Activation. Chem. - Eur. J. 2010, 16, 8376−8389. (c) Chen, S.; Li, Y.; Zhao, J.; Li, X. Chelation-Assisted CarbonHalogen Bond Activation by a Rhodium(I) Complex. Inorg. Chem. 2009, 48, 1198−1206. (d) Douglas, T. M.; Chaplin, A. B.; Weller, A. S. Dihydrogen Loss from a 14-Electron Rhodium(III) Bis-Phosphine

Dihydride To Give a Rhodium(I) Complex That Undergoes Oxidative Addition with Aryl Chlorides. Organometallics 2008, 27, 2918−2921. Bisphosphine complexes: (e) Pike, S. D.; Weller, A. S. C−Cl Activation of the Weakly Coordinating Anion [B(3,5Cl2C6H3)4]− at a Rh(I) Centre in Solution and the Solid-State. Dalton Trans. 2013, 42, 12832−12835. (f) Koenig, A.; Fischer, C.; Alberico, E.; Selle, C.; Drexler, H.-J.; Baumann, W.; Heller, D. Oxidative Addition of Aryl Halides to Cationic Bis(phosphane) rhodium Complexes: Application in C−C Bond Formation. Eur. J. Inorg. Chem. 2017, 2017, 2040−2047. (16) For O−H reductive elimination of metal-bound alkoxides, see the following. Rhodium: (a) Milstein, D. Carbon-hydrogen vs. oxygen-hydrogen reductive elimination of methanol from a metal complex. Which is a more likely process? J. Am. Chem. Soc. 1986, 108, 3525−3526. Iridium: (b) Glueck, D. S.; Winslow, L. J. N.; Bergman, R. G. Iridium Alkoxide and Amide Hydride Complexes. Synthesis, Reactivity, and the Mechanism of Oxygen-Hydrogen and NitrogenHydrogen Reductive Elimination. Organometallics 1991, 10, 1462− 1479. (c) Blum, O.; Milstein, D. Direct Observation of O−H Reductive Elimination from IrIII Complexes. Angew. Chem., Int. Ed. Engl. 1995, 34, 229−231.

E

DOI: 10.1021/jacs.8b13652 J. Am. Chem. Soc. XXXX, XXX, XXX−XXX